Quantal properties of H-type glutamatergic synaptic input to the striatal medium spiny neurons.

The striatal medium spiny neuron receives two distinct glutamatergic synaptic inputs, S-type and H-type inputs, which have very different amplitudes. We report here that peak amplitudes of unitary H-type excitatory postsynaptic currents (EPSCs) could be reduced by decreasing external Ca2+, unlike S-type EPSCs. This suggests that H-type EPSCs are multiquantal, and supports the idea that the cellular origin of H-type EPSCs is distinct from that of the S-type EPSCs.